A conventional redundancy technology implements error detection and fault redundancy functions by carrying out the same process on inputs by using plural pieces of hardware according to a required degree of redundancy and comparing outputs with one another or performing a majority decision on the outputs. Although a dual comparison system has a merit in cost compared with a triple majority decision because the number of pieces of hardware required for the dual comparison system to carry out the same process can be two, the dual comparison system cannot determine which hardware is faulty when the result of a comparison between the outputs shows that these outputs do not match each other. In contrast, although a triple majority decision system has a high cost, the triple majority decision system can determine that, when one node suffers a breakdown, the hardware which has outputted an output not matching any of the other outputs is faulty. Further, because a triple majority decision system selects a correct output as a result of performing a majority decision for a fault occurring in one piece of hardware, the triple majority decision system can mask the fault. As a conventional redundancy device, as described in, for example, patent reference 1, there is a redundancy device equipped with verification computers disposed therein, for comparing processing states and computation results in these verification computers with each other, and, when the processing states match each other and the computation results match each other, determines that the computation results are correct.